a) Field of the Invention
The invention is directed to a process and an arrangement for targeted application of a therapy beam, especially for irradiation of diseased areas in the fundus oculi of the eye (retina, choroid or sciera), in order to implement an effective radiation therapy and to protect healthy tissue as far as possible.
b) Description of the Related Art
In ophthalmology, besides other therapy systems, lasers are also used for the treatment of diseased areas in the retina and other diseased areas in the eye. In this respect, it is frequently necessary to adapt the cross-sectional shape of the treatment laser beam to the peculiarities of the irradiated region or to the shape and dimensions of the affected area. It is known in the art to enlarge or reduce a laser beam utilized in ophthalmological therapy.
For example, it is known from DE 38 23 136 C2, which describes an optical system for a fundus camera for photographing the retina by scanning with a laser beam, to change the scanning spot in the illumination beam path by means of a beam expansion system. A zoom system is provided, for example, as a beam expansion system by means of which a continuous enlargement or reduction of the beam cross section can be carried out. Other possibilities for enlarging or reducing the beam cross section consist in the arrangement of diaphragms or lenses of different diameter in the beam path. However, it is not possible to change the cross-sectional shape of the therapy beam with the means mentioned above; only the size of the cross section is changed.
In a device for generating a laser beam spot of adjustable size in the human eye according to WO 87/01819, the laser beam cross section is adapted to the diseased region of the eye to be treated in that the laser beam rotates on paths of different radii. In order to generate this laser beam spot, for example, a rotating, tilted glass plate or nutating optical element or two mirrors which can be tilted in a controlled manner are provided in the therapy beam path. In this device, it is also impossible to adapt the cross-sectional shape of the laser beam to the shape of the irradiated area in the eye.
Further, U.S. Pat. No. 5,461,212 likewise discloses diaphragms, for example, in the form of iris diaphragms, for changing the beam In a neodymium:YAG laser device, especially for ophthalmologic treatment according to DE 33 39 369, a focal optical systems formed of negative and positive lenses which are displaceable relative to one another are provided for enlarging or reducing the beam cross section.
Accordingly, it is the primary object of the invention to provide a process and an arrangement for changing the cross section of a therapy beam, especially for irradiation of diseased areas in the eye, which makes it possible to adapt not only the size of the cross-sectional surface of the beam, but also its shape, to the peculiarities of the region of the eye to be irradiated in an optimum manner and accordingly to achieve a careful treatment of the eye. In particular, this type of adaptation is desirable in photodynamic therapy of the ocular fundus and for treating age-related macular degeneration in order to protect healthy areas from the radiation.
According to the invention, this object is met in a process for changing the cross section of a therapy beam, in accordance with the invention, for targeted application of therapy radiation in the treatment of diseased areas in the eye by means of a therapy beam which is directed into the eye through an applicator. The process comprises the steps of producing an image of the fundus of the eye to be treated for determining the parameters characterizing the diseased area, deriving parameters characterizing the shape and/or size of the area to be irradiated and controlling variables from this fundus image and further processing them by a computer, controlling a control device by these parameters and controlling variables, adjusting or displacing an actuating arrangement by the control device corresponding to the shape and/or size of the area to be irradiated, and changing the shape and/or size of the cross section or changing the direction of the therapy laser beam by the actuating arrangement in a plurality of coordinates. The actuating arrangement is arranged in the beam path of the therapy beam.
Additional configurations of the inventive process and an arrangement for carrying out the process are also described.
In one embodiment of the process, the fundus of the eye to be irradiated is imaged on a CCD matrix of a CCD camera. The information is read out of the camera by a computer and further processed to obtain parameters of the region to be irradiated which characterize the shape and magnitude. Controlling variables are derived from these parameters and control an actuating arrangement arranged in the therapy beam path such that the cross section of the therapy spot at the treated area extensively corresponds to the size and shape of the diseased area in the eye.
It can also be considered as advantageous with respect to manual adjustment or adaptation of the therapy beam cross section when a fundus image of the eye to be treated is produced by means of a camera and when, on the basis of this image, the treating physician adjusts a diaphragm arranged in the beam path of the therapy beam for extensively adapting the shape and/or size of the cross section of the therapy beam passing the diaphragm to the diseased area of the eye to be irradiated.
In another advantageous modification of the process for targeted application of the therapy beam in the interior of the eye for meeting the object stated above, the fundus of the eye (e.g., the retina) is line-scanned by a target beam (separate laser source or reduced-output therapy beam source). The target beam and therapy beam traverse the same adjusting device and are consequently adapted to one another with respect to placement, size and shape. The respective position of this scanning target beam on the fundus of the eye is determined by a computer either directly from information of the CCD camera or indirectly from the actuating information of the utilized beam deflecting unit. When the position of the scanning beam is determined indirectly, signals relevant to position are obtained from the position of the deflecting elements of the beam deflecting unit by means of angle sensors and path measurement sensors and are further processed by a computer for determining the position of the target beam and therapy beam in the CCD image. If the position of the target beam lies within the area to be irradiated, the therapy beam is applied with the power needed for irradiation. When the target beam leaves the area to be irradiated, the output of the therapy beam is reduced again below the level needed for treatment.
An arrangement for targeted application of a therapy beam for irradiation of diseased areas in the interior of the eye comprises at least one radiation source for generating the therapy beam and/or a target beam, an applicator for directing the therapy beam into the eye to be treated, wherein the applicator is optically connected with the radiation sources, imaging optical elements, and an actuating arrangement for changing the shape and size of the beam cross section of the therapy beam or its direction. Further, means are provided for producing a fundus image and means are provided for obtaining shape parameters and size parameters from the area to be irradiated. These parameters are fed to a computer for processing and controlling the therapy beam with respect to output, emission duration and direction.
The actuating arrangement for changing the shape and/or size of the cross section of the therapy beam is advantageously arranged in an intermediate image plane of the therapy beam path of the applicator. A controllable diaphragm arrangement or closure arrangement by means of which the therapy beam is adapted can also be arranged in the intermediate image plane of the therapy beam path.
It is also advantageous when the actuating arrangement is a controllable LCD matrix which is arranged in the beam path in the intermediate image plane of the applicator and which is controlled by the computer in such a way that after the therapy beam has traversed the LCD arrangement or been reflected by it the cross section of the therapy beam extensively corresponds in shape and size to the surface of the diseased area of the eye to be treated.
According to an advantageous development of the arrangement according to the invention, a scanning or deflecting device which is controlled by the computer corresponding to the above-mentioned parameters is provided in the beam path of the applicator as an actuating arrangement and directs the therapy beam in a targeted manner on the area of the fundus"" to be irradiated. A scanning or deflecting device of this kind has, for example, at least one reflector which is tiltable about two axes or another beam-deflecting optical element whose position is controllable in a targeted manner depending on the above-mentioned parameters. This scanning or deflecting device is advantageously outfitted with measurement systems with which the position, e.g., of the reflector is indicated or by means of which signals characterizing the position of these reflectors are generated, which signals are then fed to the computer and further processed thereby for purposes of controlling the therapy beam.
A diaphragm with an adjustable aperture and a cover element which covers this aperture at least partially can also be provided in the intermediate image plane of the beam path of the applicator for rough adaptation of the cross section of the therapy beam to the area to be irradiated, wherein the cover element and diaphragm can be positioned relative to one another in two coordinates.
The invention will be explained more fully in the following with reference to an embodiment example.